Fuse construction



INVENTOR.

Oct. 21; 1947. w. o. SCHULTZ FUSE CONSTRUCTION Filed May 17, 1943 Will/19M 0. SCHULTZ 12 TTOEWES'.

8 5 0 5 4 9 6 3 a r 3 K/J a 3 1 1 1.1 11 11111111111 1./ 11 1 1 1 1 1 1 1 1 1 1 1 I 1 1 1 1 1 1 1 1 1 0 1 1 1 1 1 1 1 1 1 1 1 2 1 11111 11 1 1 1 1 1 1 4 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Z 4/ d .l

d I I ll x 1 1 1 1 1 1 av \x 11 111 1111 111 1 1 1 1 1 1 1 1 7 1 1/ 11 1 11 1 1 1 1 1 11 1 1 1 11 1 1 1 1 1 11 11 1 1 1 11 1/ 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 n m .5 a 6 Patented Oct. 21, 1947 UNITED STATES PATENT OFFICE FUSE CONSTRUCTION Application May 17', 1943, Serial No. 487,201

7 Claims.

This invention relates to electric fuses of the expulsion type and has to do, in part, with improvements in fuse-link assemblies and, in part, with a novelfuse cartridge and fuse-link assembly combination. It pertains more especially to fuses of the bayonet type, but its utility is not confined to fuses of that specific character.

In my co-pending application, Serial No. 485,- 099, filed April 30, 1943, now Patent No. 2,386,752, I have described and claimed a fuse construction wherein the fuse-link assembly has a built-in retractin or biasing spring, and has one terminal incorporating a so-called fishing rod which renders the fuse-link assembly temporarily extensible lengthwise, so that the extended but unstretched link assembly will more than span the entire length of the fuse cartridge. By that provision the Serviceman is enabled, without difficulty, to install a spring-biased fuse-link assembly which, except for the fishing rod, is shorter than the cartridge.

The structure of the present application is, in certain respects, considered to be a species of the invention dealt with in my aforementioned copending application, or vice versa. However, it is thought that there are certain aspects of the present invention which cannot clearly be treated as subordinate to any claimable subject matter of said co-pending application or as generic to any such subject matter, and, for that reason, it was deemed preferable to file a separate application on the present subject matter instead of including said subject matter as a part of the aforementioned application,

According to the preferred mode of carrying out the present invention, one of the fuse-link assembly terminals is threaded axis-wise to receive a correspondingly threaded screw member which is long enough to reach into the cartridge and engage the aforesaid threaded terminal, whereupon the screw member is rotated in a manner effective to tension the fuse-link assemblysaid screw member constituting an anchorage for that terminal of the fuse-link with which it is connected.

The drawings illustrate two preferred embodiments of the invention as applied to fuses of the bayonet type.

Referring to the drawings:

Fig. 1 is a sectional view, lengthwise, of a bayonet type fuse including features in conformity with the present invention;

Fig. 2 is a detail of the unstretched fuse-link assembly; and

Fig. 3 is a sectional View, lengthwise, of a modified design of bayonet fuse including a slightly different embodiment of the invention.

Referring first to Fig. 1, the fuse structure there shown includes a tubular housing I made, usually, of porcelain and intended for attachment by any suitable means to a cross-arm or other support.

ing structure. The bore of the housing is enlarged at its upper end to form a shoulder 2 upon which is seated an annular metal bushing 3 which is bored centrally to receive the fuse cartridge and effect electrical connection therewith. A gasket 4 is interposed between shoulder 2 and bushing 3 and the latter is anchored in place by means of a filler 5 of cement or low-melting alloy. A line wire connection is made to bushing 3 through the' medium of an aperture 6 and binding screw 1.

The lower end of the housing bore is similarly enlarged to form a shoulder 8 upon which is centered a second annular metal bushing 9, between which and shoulder 8 is interposed a gasket ID. The other line wire is connected to bushing 9 through the medium of aperture H and binding screw l2.

A tubular sleeve l3 made of spring sheet metal is flanged outwardly at its lower end and secured by screws [4 to the under side of bushing 9. Sleeve l3 projects upwardly, co-axially with the housing, and is slotted longitudinally for a portion of its length at several circumferentially spaced points to form a ring of contact springs which are laterally resilient and adaptive to receive and make contact with the lower terminal of the fuse cartridge.

.The functional part of the fuse comprises a fuse cartridge, identified as a whole by reference numeral [5, and a fuse-link assembly identified as a whole by reference numeral IS. The latter is shown separately in Fig. 2.

The fuse cartridge, which presently will be described, is detachably connected at its upper end to a porcelain cap I! which is designed to overlie the upper end of the housing and thus to function as a closure for excluding rain and snow from the interior of the housing. Cap I! is also designed to serve as a handle by means of which the fuse cartridge, together with the fuse-link assembly, can easily be inserted and withdrawn manually.

Seated in a recess in cap H is a centrally threaded special nut l8 which engages a stud IS, the upper end of which is secured by a nut 20 and Washer 2| bearing against a shoulder 22 formed in the cap. Stud 19 is thus rigidly anchored to cap I1 and projects downwardly therefrom as shown in Fig, 1.

Cartridge I5, with the fuse-link assembly l6 enclosed, and the cap l1, form conjointly a selfcontained unit which i withdrawable as a whole from the housing. But this unit is divisible for the purpose of replacing blown fuse-links as presently will be described.

Cartridge l5 comprises an elongate tube 23 made of horn fiber or Bakelite lined with horn fiber and is threaded externally at both ends. To the upper end of tube 23 is secured a cast bras ferrule 24, between which and the adjacent butt end of the tube is clamped a plate 25 having a hexagonal central opening the purpose of which will be explained in conjunction with the description of the fuse-link assembly.

Attached externally to ferrule 24 by means of screws 26 is a depending tubular sleeve member 27 of spring sheet metal split longitudinally at several points to form a group of contact springs which engage the bore of bushing 3 to establish electrical connection with the upper terminal of the fuse-link assembly via ferrule 24.

Encircling ferrule 24 and held in place by the tubular sleeve member 2! are a group of steel or bronze balls 28. These contact on the one side the tapered portion 24a of the ferrule and, on the opposite side the enlarged bore of bushing 3. The function of said balls is to lock the cartridge against ejection when the fuse blows. This locking mechanism constitutes the subject matter of an application of Chester W. Brown, Serial No. 466,512, filed November 21, 1942, now Patent No. 2,392,308, and assigned to the assignee of the present application.

To the lower end of tube 23 is connected a brass ferrule 29, designed to contact sleeve 13 and to establish electrical connection with the lower terminal of the fuse-link assembly, as well as an anchorage for said lower terminal.

Fuse-link assembly l6 includes a fusible section comprising a strain wire 30 and a fuse wire 3|. These are securely attached at their lower ends to an elongate terminal 32 having at its lower terminus a conical contact member 33 designed to engage the open end of ferrule 29 and to operate at the same time as a closure for said open end.

The upper ends of the fuse and strain wires are secured to a threaded stud 34 from which depends a tubular metal skirt 36 serving as a means of attachment for a fiber tube 35 enclosing the fusible section. Stud 34 is detachably connected by its thread to a coupler 37 which, in turn, serves as a means of attachment for the lower end of a retracting or biasing spring 38, as well as the lower end of a flexible conductor 39.

Attached to the upper end of spring 38 and the upper end of conductor 39 is an externally hexagonal elongate rod 40 constituting the upper terminal of the fuse-link assembly. Rod 40 is preferably made of hexagonal bar stock, and the hexagonal center opening in plate 25 is dimensioned to afford a slightly loose sliding fit for said rod. This is to prevent rotation of the rod While permitting it to pass freely through the hexagonal opening. Obviously, it is not of any vital importance that rod 40 be hexagonal. Any convenient shape or arrangement which will pre vent the rod from rotating while permitting it to move freely lengthwise will serve the purpose substantially as well.

As shown most clearly in Fig. 2, rod 40 is internally threaded throughout the greater part of its length to engage the thread of stud l9.

In Fig. 2 the fuse-link is shown with the biasing spring 38 unstretched, under which circumstance the over-all length of the fuse-link assembly is considerably less than the over-all length of the cartridge-as will be apparent from a comparison of Figs. 1 and 2.

Manifestly, the fuse-link assembly must be introduced to the bore of the cartridge through the lower end thereof; and after insertion it must be stretched in order to tension spring 38. Since terminal rod 40 is down inside the cartridge bore, the installer cannot grasp it with his fingers or with pliers. Hence the protrusion of stud I9 is made of sufficient length to reach into the upper end of the cartridge and engage the thread of terminal rod 40, whereupon the cartridge is rotated relatively to cap 17 in a direction to screw stud I9 into rod 40. This, of course, causes an upward movement of terminal rod 40 with a consequent tensioning of the biasing spring. It will be seen that the upper extremity of ferrule 24 is introverted to form a shoulder against which the upper end of terminal rod 40 abuts when the fuselink assembly is stretched to the prescribed degree. When the rod 40 is in clamped relation to the shoulder on the upper end of the ferrule 24, it forces the upper end of the ferrule into clamped relation to the nut l8 on the stud l 9, thereby detachably mounting the cartridge on the cap ll.

It is to be understood that the operation of replacing a fuse-link assembly is performed with the fuse cartridge withdrawn from the housing.

When the fuse blows the biasing spring quickly retracts stud 34 while the lower fuse-link terminal 32 is blown downwardly out of the cartridge. Thus, a quick separation of the arcing fuse terminals is effected.

It will be seen that there is no fuse-link anchorage in the external peripheral surface of the cartridge to obstruct insertion and withdrawal of the cartridge into and from the housing; and also it will be noted that the bore of the cartridge is completely closed against intrusion of insect pests.

The fuse structure of Fig. 3 is substantially identical with that of Fig. l-except as will be pointed out-and identical parts are designated by the same reference numerals. This modification is predicated largely upon the structure illustrated by Figs. 5, 6, and 7 of my co-pending ap plication, Serial No. 467,121, filed November 27, 1942, now Patent No. 2,416,243, and assigned to the assignee of the present application. In this instance the stud E9 of Fig. 1 has been replaced by a stud 41 having a head 42 permanently affixed which abuts the top of ferrule 43.

The clutch and lock mechanism here shown is fully described in my aforementioned application Serial Number 467,121 and for that reason will not be elaborately described here. But, briefly, it comprises a group of ball-like rollers 44 corresponding in function to balls 28 of Fig. 1, together with a tubular skirt-like member 45 of spring sheet metal which serves as a retainer for rollers 44 as well as a resilient contact member for establishing electrical connection with bushing 3, and a helical spring 46 bearing against the top of head 42. The latter spring tends to push the fuse cartridge downwardly away from cap I'l, but permits a limited relative upward movement of the cartridge in response to recoil force engendered by blowing of the fusewhich relative movement causes rollers 44 to pressingly engage the adjacent bore of bushing 3, thereby momentarily locking the cartridge and consequently preventing it being blown out of the housing while at the same time not interfering with normal withdrawal of the cartridge from the housing.

Spring 46 is secured to an insert 41, which latter is anchored in cap 17; and ferrule 43 is detachably connected to member 45 by means of bayonet slots in said member which engage individually the several rollers 44. The bayonet slots are not shown here, but are fully illustrated in my aforementioned application Serial No. 467,121.

' important.

The modified form of the invention depicted in Fig. 3 is'rnore satisfactorily adaptable to the species of clutch and lock mechanism there'shown than is that embodiment of the invention shown in Fig. 1. But functionally the two embodiments are alike, as respects the problem of installing the fuse-link assembly.

What is claimed is:

l. The combination with a fuse cartridge, of a fuse-link assembly mounted within said cartridge and having a pair of spaced terminals anchored respectively at the two ends of said cartridge, one of said terminals being threaded lengthwise, the length of said fuse-link, when unstretched, being substantially less than the length of the cartridge, wherefore the free endv of said threaded terminal is situated Well within the bore of the cartridge and well beyond the nearest end of the cartridge when the unstretched fuse-link assembly is fully inserted in the cartridge bore, and a screw having a thread engageable with the thread of said threaded terminal, said screw being long enough to reach into the bore of the cartridge to engage said threaded terminal and then operative by rotation to tension the fuse-link assembly, said screw being also arranged to function as an anchorage for the threaded terminal for maintaining the fuse-link assembly under tension.

2. The combination with a fuse cartridge of a fuse-link assembly extending lengthwise of said cartridge within the bore thereof and having a first terminal anchored to one end of the cartridge and a second terminal anchored near the other end of said cartridge within said bore, said assembly also including a fusible section and a biasing spring in series interconnecting said terminals, said second terminal being threaded internally lengthwise of the fuse-link assembly, means operative to prevent rotation of said second terminal relatively to said cartridge while permitting lengthwise movement thereof, said fuse-link assembly, when unstretched, being considerably shorter than said cartridge, and anchoring means for said second terminal including a screw capable of reaching into the cartridge bore and there engaging the thread of said second terminal when said fuse-link assembly is unstretched, said screw being operative by rotation to move said second terminal lengthwise to stretch the fuse-link assembly, said anchoring means abutting the end of the cartridge remote from said first terminal for opposing the tension of said spring.

3. In combination, a fuse cartridge comprising an elongate tube of dielectric material, a ferrule secured to one end of said tube and having a discharge passageway registering with the bore of said tube, a second ferrule secured to the other end of said tube, said second ferrule extending lengthwise of said tube and having a central passageway extending therethrough co-axially with the tube bore, a member secured between one end of said tube and said second ferrule and having a non-circular opening aligned With the bore of the tube, a fuse-link assembly extending lengthwise within the cartridge and having a first terminal anchored to said first ferrule and a second terminal anchored Within said second ferrule, said second terminal being externally non-circular to conform to the non-circular opening in said member and being slideable lengthwise, but not rotatable therein, a fusible section and biasing spring in series interconnecting said terminals, said second terminal being threadedlengthwisaand anchoring means for said second terminal having a threaded port-ion capable of reachin into the cartridge bore and there engaging the thread of said second terminal and operative by rotation to move said second terminal lengthwise to tension the fuselink assembly.

4. In a fuse structure, a tubular housing of insulating material open at both ends and having ingan elongate tube of dielectric material to:

gether with a first ferrule attached to one end of the tube and a second ferrule attached to the other end of the tube, said ferrules engaging said contact members individually, one end of said second ferrule abutting said closure cap centrally thereof and having an introverted flange forming an annular shoulder interiorly of said second ferrule and co-axial therewith, a threaded stud anchored to said closure cap and projecting into said second ferrule through said flange, a fuse-link assembly within the bore of said cartridge and extending lengthwise thereof, said assembly including a first terminal engaging said first ferrule, a second terminal within and contacting said second ferrule, a fusible section and biasing spring in series interconnecting said terminals, said second terminal being threaded lengthwise for engagement by said stud, the latter serving as an anchorage for said second terminal and holding the same against said shoulder to clamp the cartridge to said closure cap and to maintain the fuse-link assembly under tension.

5. In a fuse, the combination with a cartridge comprising an insulating tube, a first contact at one end of said tube having a bore therethrough constituting an extension of the bore of said tube and providing an internal contact shoulder, and a second contact at the other end of said tube including fuse link engaging means, of a fuse link comprising first, second, and third terminals, a fusible member interconnecting the first and second terminals, a tensioning spring connecting the second and third terminals, said first terminal engaged with the second contact on said tube and said third terminal including a contact portion engaging said shoulder in the first contact and a threaded extension projecting out of said first contact and means comprisg a nut on said threaded extension for normally holding said contact portion in firm engagement with said shoulder, said third terminal contact portion and said threaded extension forming conjointly an expansible and contractible means for facilitating the insertion of said fuse link within said cartridge.

6. In a fuse, the combination with a, cartridge comprising an insulating tube, a first contact at one end of said tube having a bore therethrough constituting an extension of the bore of said tube and providing an internal contact shoulder, and a second contact at the other end of said tube having a bore constituting an extension of the bore of said tube and terminating in a conelike flare, of a fuse link comprising first, second, and third terminals, a fusible member interconnecting said first and second terminals, a tensioning spring connecting said second and third terminals, said first terminal including a cone-like contact portion engaging said flare, and said third termina1 including a contact portion engaging said shoulder in the first contact and a threaded extension projecting out of said first contact, and means comprising a, nut on said threaded extension for normally holding the last mentioned contact portion in firm engagement with said shoulder, said third terminal contact portion and said threaded extension forming conjointly an expansible and contractible means for facilitating the insertion of said fuse link within said cartridge.

'7. The combination with a fuse cartridge comprising an insulating tube and a conductive contact apeitured coaxially therewith, of a fuse link assembly mounted within said cartridge and including a pair of spaced terminals connected by a fusible section, one of said terminals being 20 8 threaded lengthwise and telescopically movable in and non-rotatively held in said contact, and a threaded member extending through said aperture in said contact and engaging the threads of said one terminal, said member being rotatably supported by said contact for rotation relative to said one terminal.

WILLIAM O. SCHULTZ.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 22,343 Ramsey July 6, 1943 1,818,382 Conrad Aug. 11, 1931 2,091,453 Ramsey Aug, 31, 1937 1,907,581 Ramsey Mar. 9, 1931 

